Portable radio compass



Dec. 26, 1950 M. o. ERCOLINO PORTABLE RADIO COMPASS Filed June 5, 1945 TOUCH-TO-SENSE CONTACT OPERATOR FUNCTIONS AS SENSE ANTENNA 1 TURN 4 TURNS TO A 2 RECEIVER m. N E M 4 H c w T a m N 0 c INVENTOR. MICHAEL D. ERCOLINO ATTORNEY Patented Dec. 26, 1950 PORTABLE RADIO COMPASS Michael D. Ercolino, Asbury Park, N. .L, assignor to the United States of America as represented by the Secretary of War Application June 5, 1945, Serial No. 597,682

5 Claims. (01. 343-113) (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

My invention relates to a radio compass, particularly one which is portable and can be readily used with a conventional communication receiver without alteration thereof.

One conventional type of radio compass combines a directional antenna having a figure-ofeight response pattern, such as a loop, with an omnidirectional sense antenna, such as a vertical antenna, to derive a resultant cardioid pattern so that the direction of an incoming wave can be determined without ambiguity.

It is a principal object of my invention to simplify the radio compass of the above mentioned type.

It is a further object of my invention to provide a radio compass of this type in which the usual sense antenna can be dispensed with, thereby rendering it particularly suitable in portable equipment.

Another object of the invention is to provide a radio compass in which the need for providing an accurately balanced loop antenna is obviated.

In accordance with my invention the body of the operator is utilized as an omnidirectional sense antenna, thereby reducing the cost or" the equipment and'rendering it more portable. The

equipment comprises a portable receiver and a loop antenna both carried by the operator. The loop antenna is held aloft and oriented by the operator until a null or minimum signal is obtained. A contact is located near the loop handle so that it can be easily contacted by the thumb of the operator, whereupon the body becomes connected into the circuit and acts as a sense antenna whereby the 180 ambiguity in bearing can be resolved.

To compensate for unbalance in the coupling between the loop antenna and the sense antenna, an unbalanced autotransformer is used for coupling the antenna circuits to the receiver.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, wherein:

Figure l is a perspective View of the entire equipment and shows the loop antenna held in operating position by an operator, and

Figure 2 is a schematic circuit diagram or the invention.

Referring now to Fig. l, the radio compass which constitutes my invention is shown carried by an operator A, who also forms a part of said equipment. The radio compass comprises a loop antenna B, which in practice is collapsible when not in use. The loop is connected by means of a shielded cable C to the combination receiver and transmitter E through an impedance-matching autotransformer unit D. On the handle of the loop is a metallic contact It] in a position to be readily contacted by the thumb of the operator, whereby the body functions as a vertical sense antenna.

Referring now to Fig. 2, loop B comprises two coaxial coils l2 and I l which are electromagnetically coupled to each other. Coil i2 constitutes the loop proper and consists of several turns, in this case four, the total number depending, of course, on the frequency range of the equipment. A small variable condenser H5, situated in the base of the loop, is used to tune coil l2 to the frequency of the incoming signal.

The contact I0 to which the sense voltage is connected, as shown, to one side of condenser it, preferably at the leading end of the loop. It will be noted that, with this arrangement, the loop is floating with respect to ground and the sense voltage is applied to coil [2 at a point which is not at the electrical center thereof, i. e. at a point which is asymmetrical with respect to all portions of said loop. It would, in any case, be difiicult in practice to balance the loop se that the touch-to-sense contact IE at the handle of the loop would appear at the electrical center thereof.

To compensate for this unbalance, the coil I2 is coupled to the receiver through a one-turn link coil it which is connected through a cable C and separable connector G to the primary situated at one end of an autotransformer 23. The electrical center of this primary is tapped and connected to ground. A tuning condenser 22 is connected between ground and the high potential side of coil 25, which is also connected, through lead 2 5, to the antenna input circuit of the receiver portion of component E. In this case, the lead as is clipped directly to the collapsed, telescopic antenna (not shown) which forms a regular part of'component E.

As thus connected, it will be seen that the primary section of auto-transformer 20 is unbalanced with respect to ground so that a resultant unbalance voltage with respect to ground exists- By properly phasing this voltage it can be made to oppose the unbalance in the loop l2 so that the overall voltage in the entire loop circuit is balanced.

The above described loop circuit is applicable to systems using any type of sense antenna; and the vertical, omnidirectional antenna A, shown in dotted lines, is tobe understood as indicating either the use of such ordinary sense antenna or the use of the body of the operator for this purpose, as illustrated in Fig. 1.

From the above description, it will be seenthat- I have provided a novel radio compass system including means whereby the operator can be connected into the loop circuit to act as a sense antenna, thus reducing the cost of the equipment, enhancing its portability, and reducing. servicing requirements. In addition there has been described a novel couplin system which obviates the necessity of providing a. balanced loop- While there has been described what is at present considered a preferred embodiment of the invention, it will be obvious to those skilled in. the art that various changes and modifications may be made therein without departing from the invention, and it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of. the invention.

1. A radio compass attachment for a portable receiver comprising a portable antenna having a figure-of-eight response pattern and having a handle adapted to be grasped by one hand of the operator to hold the antenna aloft in operating position, and a metallic contact coupled to the circuit of said antenna and located adjacent said handle whereby said contact can be conveniently touched by the thumb of said hand to couple the body'of the operator to the loop antennacircuit, whereby said operator functions as a vertical sense antenna- .2. A radio: compass circuit for a receiver comprising a loop connected in series with a variable tuning means therefor, an omnidirectional antenna, means to couple said. omnidirectional antenna to said loop,. and means to couple said loop to said receiver, said last-named means including an unbalanced autotransformer to compensate for any asymmetry in the coupling of said antenna to said loop.

3. A radio compass for a radio receiver comprising a loop connected in series with a variable tuning condenser, means for connecting an omnidirectional antenna to one side of said condenser, and means to couple said loop to said receiver, said coupling means including a second loop electromagnetically coupled to said first p, an autotransformer having a primary at one end thereof coupled to said second loop, said primary having a grounded center-tap, means for coupling the secondary of said autotransformer to the input'cincuit of said receiver, and a variable tuning condenser connected between the other end of said'secondary and said center-tap.

e. A portable radio compass for a radio receiver, comprising a portable directional antenna coupled to said receiver and having an ambiguous response pattern, a. handle on said antenna adaptedv to be grasped by the hand of an operator to hold said antenna in operating position, and a contact in the vicinity of said handle so that it can be touched by said hand while holding said. antenna, said contact being so coupled to said loop that the body of the operator functions as an omnidirectional sense antenna.

5'. A portable radio compass as set forth in claim 4 wherein the coupling, between said antenna and said receiver includes an unbalanced transformer to compensate for any asymmetry in the coupling of said body to said loop.

MICHAEL D. ERCOLINO.

REFERENCES CITED The following references are of record in the file of this patent:v

UNITED STATES PATENTS Number Name Date 876,165 .De Forest Jan. 7, 1908 948,086 Bellini et al' Feb. 1, 1910 1,486,049 Spring Mar. 4, 1924 1,640,929 Farkouh. Aug. 30, 1927 2,207,244 Dolbear July 9, 1949 2,220,087 Dolbear l Nora-5,1940 2,255,897 Rebori. et al. Sept. 16, I941 2,319,627 Perlman lVIay 18, 1943 

